You'll probably get between 80 and 82% efficiency if you get your pH just right. You might improve the flavor of your beer if your original pH was off by a lot.
Seems to me you've probably been lucky and your pH was already 5.2-5.5 without measurement, so then your efficiency won't change at all. It will only improve if pH was far off.
Interesting, as it seemed to have made a rather large difference in my efficiency. I went from making a 6.2% IPA to a 7% IPA with no changes whatsoever to the recipe/process except for dialing in mash pH. Brewhouse efficiency went from <65% to >70% with nothing more than some Lactic acid additions.